There is no sludge around the oil filler cap or anything like that!
That's usually the sign of a blocked breather, and can happen if you use the car on short jorneys this may appear.
I had a look at the fan switch and the connector looked a bit dodgy but the fan was coming on but it didnt look as if it was going as fast as it usually does!
Change the fan switch connector if possible, if the fan is not running correctly then there is your problem....and also check that the temperature sender on the head is not all manky and giving you a dodgy reading
